# `GeoGenius.SeededMatch`
[🔗](https://github.com/agoodway/geo_genius/blob/main/lib/geo_genius/seeded_match.ex#L1)

One area returned by a plural catalog read, paired with the seed that found
it.

The plural reads -- `GeoGenius.children_of_many/2` and its siblings --
resolve many seeds in one call, so the seed has to travel with each row:
without it a caller cannot tell which of its thousands of inputs a given row
answers. `match` is the ordinary `GeoGenius.AreaMatch` struct the singular
reads return, unchanged, so everything documented about it still applies.

`seed_key` holds whichever kind of seed the read takes: an area key for
`children_of_many/2`, `ancestors_of_many/2`, and `related_areas_many/2`, and
a code value for `areas_by_code_many/3`.

Grouping a plural result back onto the caller's own list is one step:

    GeoGenius.children_of_many(county_keys)
    |> Enum.group_by(& &1.seed_key, & &1.match)

A seed that matched nothing is absent from the result rather than present
with a nil match, so a caller that needs every seed represented supplies its
own default.

# `t`

```elixir
@type t() :: %GeoGenius.SeededMatch{
  match: GeoGenius.AreaMatch.t(),
  seed_key: String.t()
}
```

# `from_result`

```elixir
@spec from_result(Postgrex.Result.t()) :: [t()]
```

Maps a plural read's query result into structs.

The seed column is located by name and split off; everything left is handed
to `GeoGenius.AreaMatch.from_result/1`, which maps it by name in turn. A
positional split would put an area key in `:seed_key` and a seed in
`:area_key` the first time the projection moved, and both are plausible
strings.

Raises if the result carries no seed column: that is a projection bug to
fix, not a value to invent.

---

*Consult [api-reference.md](api-reference.md) for complete listing*